It is conventionally known that a yarn is wound onto one of two spindles parallelly installed in a winding apparatus to form a package on a bobbin inserted on the spindle and that, when a full package is completed, the yarn is changed to the other spindle. Due to the above-described method, a yarn can be continuously wound onto bobbins without causing interruption in the winding of the yarn, and as a result, operational efficiency can remarkably be increased. In this winding method, it is very important that the yarn change from one spindle to the other spindle when a full package is completed be ensured. In this case, if the success ratio of the bobbin change is low, the advantages created by the above-described continuous winding method are reduced.
Japanese Patent Publication No. 34420/70 discloses that in order to increase the success ratio of the bobbin change, a specially designed yarn threading device enclose each spindle so as to guide a yarn around the spindle. However, such a yarn threading device is excessively large and does not comply with the requirement for saving space.
A device has been proposed in Japanese Patent Application Laid-open No. 93141/79 by which the above-described specially designed yarn threading device can be omitted and in which a traverse device is simplified, and as a result, the size of the obtained device is minimized. More specifically, in this prior art device, a yarn guide is swingably disposed at the front end of a swingable arm, and the arm is tilted toward a spindle to which the yarn passage is changed, so that a yarn guided by the yarn guide disposed at the front end of the arm comes into contact with the empty bobbin. As a result, a yarn is caught by the yarn threading portion formed at the position adjacent to the end of the empty bobbin while the yarn is axially moved onto the empty bobbin.
According to the proposal in Japanese Patent Application Laid-open No. 93141/79, the compactness of the construction in the yarn winding apparatus can be achieved, however, the success ratio of the bobbin change becomes low because of the following reasons. In this prior art device, a traverse device which can effect usual traverse motion is utilized to perform a threading operation. Accordingly, the traverse device described in this prior art is required to function so that a yarn is uniformly distributed around the bobbin by means of the traverse motion. In short, in this prior art device, the traverse motion remains while the bobbin change operation is effected. Accordingly, the yarn must necessarily be in contact with the bobbin and axially be moved for a short time before it is caught by the yarn threading portion located adjacent to the bobbin end. When a yarn is moved while it is still in contact with the bobbin, as described above, the tension in the yarn becomes unsteady, and the yarn may not be caught by means of the yarn threading portion.